Superheated Steam Generator Research Articles

Transient thermal hydraulic analysis of a small passive lead–bismuth eutectic cooled fast reactor

The lead–bismuth eutectic cooled fast reactor (LFR) emerges as a cutting-edge technology in nuclear reactor design. This study introduces a compact, passive, and long-life LFR reactor LFR-180. The LFR-180 incorporates modular helical-coiled once-through steam generators (H-OTSG) and direct reactor auxiliary cooling systems. This integration enables the generation of superheated steam and passive safety features of the LFR-180, eliminating the necessity for a water-steam separation device and contributing to enhanced power generation efficiency. A detailed transient thermal hydraulic analysis is conducted with tailored models for LBE solidification and H-OTSG thermal hydraulics. Results demonstrate that LFR-180 is a fully passive reactor, requiring no intervention up to 149.1 h after shutdown. The H-OTSG can serve as the heat exchangers of the active safety systems that can effectively reduce the peak core outlet temperature from 1003.6 K under the SBO accident to 724.2 K after shutdown.

Mechanism of the rapid generation of superheated and saturated steam using a water-containing porous material

Superheated steam (SHS) is employed in various fields for everyday activities and industrial production, e.g., drying, cleaning, and reaction engineering. Although a facile method for realizing rapid SHS and saturated steam generation from water-containing porous materials has been proposed, with a second order start-up/cut-off response time and high energy utilization efficiency, the mechanism of this rapid SHS generation has not been clarified despite the proposition of a two-step process, including heating-based evaporation beneath the wire heater and reheating in the flow path. In this study, further experiments were conducted to separately consider both heating processes. The steam temperature directly beneath the wire heater correlated well with the film temperature, which is equal to the average temperature of the wire heater and the saturation temperature of the surface of the porous material. The measurement results of the temperature distribution inside the porous material block as well as the results of the electrical resistance directly beneath the wire heater revealed that no dry-out area was formed directly beneath the wire heater during SHS generation. Further, the three-dimensional laser scanning results revealed significant roughness on the surface of the porous material. The narrow gap, which was formed between the wire heater and the surface of the porous material, was critical to SHS generation, and the detailed mechanism was presented.

Numerical investigation and comparison of tubular solar cavity receivers for simultaneous generation of superheated steam and hot air

Solar cavity receivers are a crucial technology to transform solar energy into easily usable thermal energy. Various cavity receiver structures employing helical absorber tubes were investigated to provide either superheated steam or hot air efficiently. However, few studies have focused on receivers that generate both hot fluids simultaneously. The simultanoues generation can lead to a more compact and cheaper system, and can be used for applications such as a high-temperature electrolysis to produce green hydrogen or syngas. In our study, three different tubular solar cavity receivers were proposed and numerically investigated. Each receiver consists of three different processes: (1) water evaporation, (2) superheating steam, and (3) heating air. The 1D-3D model developed in our previous study was used to investigate the various aspects such as lamp-to-thermal (solar simulator was used as a light source) and exergy efficiencies. The numerical results have proven that the receiver employing both cylindrical and conical helical tubes can obtain the highest lamp-to-thermal (67.0%) and exergy efficiencies (46.9%). A parameter study was also conducted based on the chosen optimal receiver. The obtained results can become a basis for further implementation, and especially the use in high-temperature electrolysis could become crucial in a future energy system.

Thermal and flow characteristics of a cylindrical superheated steam generator with helical fins

Thermal and flow characteristics of a cylindrical superheated steam generator with helical fins

Optimal Design of High-Frequency Induction Heating Apparatus for Wafer Cleaning Equipment Using Superheated Steam

In this study, wafer cleaning equipment was designed and fabricated using the induction heating (IH) method and a short-time superheated steam (SHS) generation process. To prevent problems arising from the presence of particulate matter in the fluid flow region, pure grade 2 titanium (Ti) R50400 was used in the wafer cleaning equipment for heating objects via induction. The Ti load was designed and manufactured with a specific shape, along with the resonant network, to efficiently generate high-temperature steam by increasing the residence time of the fluid in the heating object. The IH performance of various shapes of heating objects made of Ti was analyzed and the results were compared. In addition, the heat capacity required to generate SHS was mathematically calculated and analyzed. The SHS heating performance was verified by conducting experiments using the designed 2.2 kW wafer cleaning equipment. The performance of the proposed pure Ti-based SHS generation system was found to be satisfactory, and SHS with a temperature higher than 200 °C was generated within 10 s using this system.

Experimental Study and Thermal Diffusivity Analysis on Whiteness Reduction of Natural Fiber Fabric Treated with Superheated Steam

ABSTRACT The family use garment steamers with superheated steam have several advantages but lead natural fiber fabrics whiteness reduction. This study explored the four kinds of natural fiber fabric whiteness reduction both experimentally and theoretically. We first built a temperature controllable 1 atm superheated steam generator, and recorded the whiteness and decrease percentages of cotton, flax, silk and wool fabrics at 150°C, 175°C, and 200°C separately. Then we calculated the monotonically increases thermal diffusivity(α) as a function of fiber volume fraction(), and the α is divided into three regions based on the : average region( <0.3), transition region(0.3 < <0.9) and fiber region( >0.9). The of studied samples are all in the average region, and the whiteness reduction percentage value sequence is opposite with the α, which are a reflection of the samples average properties, which means the design of superheated fabric steamers should depend on the structures or garment types of fabrics rather than fiber types.

Start-up strategy of a diesel reformer using the decomposition heat of hydrogen peroxide for subsea applications

A diesel reformer start-up strategy using hydrogen peroxide (H2O2) decomposition heat is first proposed for subsea applications such as submarines and unmanned underwater vehicles (UUVs), requiring no oxygen. H2O2 can supply not only both the oxygen and steam required for the diesel autothermal reforming (ATR) reaction but also heat via the catalytic H2O2 decomposition reaction. We utilize the high-quality heat from H2O2 for the reformer start-up by evaporating and chemically decomposing the 50 wt% concentration H2O2. A comparative reformer start-up strategy study is performed between conventional diesel ATR and diesel-H2O2 ATR using a 1 kWe-class diesel reformer. For the conventional start-up, three steps of partial oxidation, partial load ATR, and full load ATR are required to heat the ATR reformer after electrically preheating the ATR catalyst. However, the proposed strategy requires only one full load ATR step after preheating the ATR catalyst using H2O2 decomposition heat. With the suggested start-up strategy, a simplified sequence with negligible temperature fluctuations and a 57% start-up time reduction are achieved. We find it significant that the full load flowrate of superheated steam generation from the H2O2 decomposer is a critical factor in simplifying and shortening the start-up procedure.

Thermodynamic, exergoeconomic, and environmental evaluation of a new multi-generation system driven by a molten carbonate fuel cell for production of cooling, heating, electricity, and freshwater

Because of the ever-growing demand for energy in today’s world, new efficient multi-generation systems are much sought after. Analyzing the practicality and performance of such innovative systems, especially ones utilizing novel energy conversion technologies, has been a popular subject among scientists. In this paper, a comprehensive assessment of a novel multi-generation system driven by a molten carbonate fuel cell is presented from thermodynamic, exergoeconomic, and environmental viewpoints. The proposed system consists of a molten carbonate fuel cell for electricity generation, a heating process heat exchanger for superheated steam generation, a generator-absorber heat exchanger cycle for generating cooling load, and a desalination subsystem for producing freshwater. To investigate the performance of the system, the influences of two important parameters, namely current density and fuel cell operating temperature, are studied on the generated cell voltage as well as the production rates of the products, the energy and exergy efficiencies, the cost rate, the cost per unit exergy, and the carbon dioxide emission rate. According to the results, the net electrical power production and the energy and exergy efficiencies of the proposed system are 1439 kW, 79.9%, and 51.9%, respectively. Also, the investment cost rate of the system is 30.4 $/h, which results in the production of the mentioned outputs with a total cost per unit exergy of 21.6 $/GJ. Moreover, the carbon dioxide emission rate of the system is found to be 247 kg/MWh.

High-Efficiency Superheated Steam Generation for Portable Sterilization under Ambient Pressure and Low Solar Flux.

Superheated solar steam generation above 100 °C is critical for many important applications such as sterilization but is challenging to achieve under natural fluctuating low-flux solar illumination and often requires pressurization and the usage of expensive optical concentrators. Herein, we demonstrate generation of superheated steam under ambient pressure and low-flux solar illumination by integrating a recently emerged interfacial evaporation design into a solar vacuum tube. Within the tube, the water vapor, which is generated by a high-efficiency localized heating-based evaporator, is further heated by a heat exchanger into superheated steam without pressurization. The steam generator has shown tunable steam temperature from 102 to 165 °C and solar-to-steam conversion efficiency from 26 to 49% under 1 sun illumination. Owing to the minimized heat loss from the solar vacuum tube and the interfacial evaporation design, it enables stable generation of steam above 121 °C under ambient fluctuating solar illumination with an averaged solar flux of ∼600 W/m2. Effective sterilization is verified using both the Geobacillus stearothermophilus biological indicator and Escherichia coli bacteria, making portable solar steam sterilization and other steam-related applications feasible under ambient solar illumination.

Experimental study on superheated steam generation by the reaction of high humidity hydrogen and oxygen in a model internal combustion steam generator

ABSTRACTInternal combustion steam cycle (ICSC) is a novel steam power cycle using hydrogen as an energy carrier to produce superheated steam. High humidity hydrogen produced during fast hydrogen production process is directly used to produce superheated steam by combusting with stoichiometric oxygen without hydrogen storage. The ICSC efficiency is greatly affected by the content of non-condensable gas in superheated steam. In the present study, superheated steam generation by high humidity hydrogen was investigated in a model internal combustion steam generator. Effects of H2O/H2 molar ratio of humid hydrogen and velocity ratio of humid hydrogen to oxygen on non-condensable gas content, combustion efficiency, and mixing rate were evaluated. The results showed that the critical H2O/H2 ratio for the humid hydrogen humidity limit was 2.8. With increasing velocity ratio, mixing rate and combustion efficiency increased under the same H2O/H2 ratio. The H2O/H2 reaction rate monotonously decreased as the H2O/H2 ratio increased from 1.0 to 2.5, while the mixing rate increased along with the velocity ratio. The combustion efficiency initially increased and subsequently decreased, and the peak value was reached at a H2O/H2 ratio of 1.75. This result indicated that the humid H2-O2 combustion was controlled by diffusion under H2O/H2 ratios of 1.0 to 1.75, but turned to be controlled by chemical kinetics when the H2O/H2 ratio ranged between 1.75 and 2.5.

Pre-test analysis of protected loss of primary pump transients in CIRCE-HERO facility

In the frame of LEADER project (Lead-cooled European Advanced Demonstration Reactor), a new configuration of the steam generator for ALFRED (Advanced Lead Fast Reactor European Demonstrator) was proposed. The new concept is a super-heated steam generator, double wall bayonet tube type with leakage monitoring [1]. In order to support the new steam generator concept, in the framework of Horizon 2020 SESAME project (thermal hydraulics Simulations and Experiments for the Safety Assessment of MEtal cooled reactors), the ENEA CIRCE pool facility will be refurbished to host the HERO (Heavy liquid mEtal pRessurized water cOoled tubes) test section to investigate a bundle of seven full scale bayonet tubes in ALFRED-like thermal hydraulics conditions. The aim of this work is to verify thermo-fluid dynamic performance of HERO during the transition from nominal to natural circulation condition. The simulations have been performed with RELAP5-3D© by using the validated geometrical model of the previous CIRCE-ICE test section [2], in which the preceding heat exchanger has been replaced by the new bayonet bundle model. Several calculations have been carried out to identify thermal hydraulics performance in different steady state conditions. The previous calculations represent the starting points of transient tests aimed at investigating the operation in natural circulation. The transient tests consist of the protected loss of primary pump, obtained by reducing feed-water mass flow to simulate the activation of DHR (Decay Heat Removal) system, and of the loss of DHR function in hot conditions, where feed-water mass flow rate is absent. According to simulations, in nominal conditions, HERO bayonet bundle offers excellent thermal hydraulic behavior and, moreover, it allows the operation in natural circulation.

Investigation of density wave instability in once-through superheated steam generators using SIGHT

Density-wave oscillation is the most common type of two-phase flow instability in the steam generators. A computer code SIGHT was derived to study on flow instability for the superheated steam generator under high pressure. The drift flux model was used for two-phase flow analysis. Linear, frequency-domain method was used for modeling and the flow stability was evaluated by Nyquist stability criterion. The unified and representative variables, namely water/steam mass flow density, water/steam enthalpy and liquid sodium temperature were selected to describe steady state and perturbations. The density perturbation of subcooled water was taken into account since the large subcooling degree of feedwater. The code has been tested against the existing experimental data and compared with results of past analysis code. Also the effect on flow stability caused by system parameters and density changes in subcooled water was analyzed. Lastly, preliminary stability thresholds were given for Steam Generator of China Fast Reactor 600 (CFR600) using SIGHT.

Life cycle assessment of superheated steam drying technology as a novel cow manure management method

Common methods of managing dairy manure are directly applying it to the farm field as a fertilizer. For direct application without any type of treatment, the majority of nutrients in the manure run off to the local river and lake during precipitation periods. The algae bloom is one of the environmental outcomes due to eutrophication of the lakes, which may jeopardize the quality of drinking water. In this study, superheated steam drying (SSD) technology is investigated as an alternative manure management method. Rapidly dried cow manure can be used as alternative fuel. Evaluations of energy payback time (EPBT) and life cycle assessment (LCA) of the SSD technology are presented in the SSD scenario and the results are compared with those of the direct field application (FA) of fresh manure and anaerobic digestion (AD). The heat required for the generation of superheated steam in the SSD scenario is provided from combustion of the dry manure to reduce energy costs. The results for the SSD process show 95% and 70% lower eutrophication and global warming potential in comparison to the FA scenario. Acidification potential for SSD turned out to be 35% higher than FA. The comparison of SSD with AD for their EPBT and normalized impacts indicated that the proposed SSD scenario has higher environmental sustainability than AD (70% lower impact), and is likely an economically better choice compared to conventional AD method (87% lower EPBT) for the future investment.

Advances in autothermal reformer design

Together with the high-temperature polymer electrolyte fuel cell, the reactor for the autothermal reforming (ATR) of liquid hydrocarbons, such as diesel fuel or kerosene, is the key component of the Jülich fuel cell system in the 5kWe power class. This paper presents some of Jülich’s most recent development in the field of ATR reactors, specifically the ATR 12. ATR 12 is characterized by a new concept for the internal generation of superheated steam as one of the ATR reactants using concentric shells instead of coiled tubing and particularly by the integration of an electric heating wire to enable fast and autonomous start-up. Three different experimental procedures for heating up the ATR 12 are presented and discussed, the most suitable of which enables the start-up of the ATR 12 within approximately 15min. As a consequence, from the system perspective, the bulky start-up burner, which is also difficult to control, along with the corresponding heat exchanger unit, can be dispensed with. Additionally, comprehensive steady-state experiments identify suitable reaction conditions for the operation of the ATR 12.

Coupling waste heat extraction by phase change materials with superheated steam generation in the steel industry

To allow a better exergy exploitation than the current state-of-the-art waste heat to power solutions in the steel industry, a new type of energy recovery system based on Phase Change Materials is proposed. In particular, the use of high temperature PCMs evolves from simply smoothing off gas temperature, as in the most recent studies for energy recovery from electric arc furnaces, to generating constant superheated steam able to feed the downstream turbine nearly at nominal load. This result is achieved by introducing an auxiliary section between the PCM Section and the steam generation one, which provides the auxiliary heat needed to level the thermal content of off gas. The auxiliary heat is extracted from the PCM units by a heat transfer fluid flowing across the inner tube of each PCM container.Different models to properly size and simulate the operations of the proposed energy recovery system have been developed and integrated. Results show how the size of the steam generator and the turbine can be reduced of about 41% with respect to traditional solutions, while increasing electric power production by 22% thanks to the reduced fluctuation in steam parameters at the turbine inlet, which leads to a greater overall efficiency.

Investigation on corrosion failure of Cr–Mo P11 grade pipe in primary section of a superheated steam generation system

This paper presents failure analysis of corroded steam pipes (Cr–Mo, P11 grade) at ammonia production plant. The corrosion and deposition morphologies are characterized using scanning electron microscopy. In addition, elemental composition analysis of deposited corrosion products is carried out using energy dispersive X-ray. This study clearly indicates the sensitivity of P11 grade steel pipe to intensive oxygen corrosion in steam generation systems with improper implementation of deoxygenating processes. Furthermore, this pipe grade and oxide layer on its surface are susceptible to cracking at the presence of high-level thermal stresses.

Thermodynamic and economic evaluation of a solar aided sugarcane bagasse cogeneration power plant

This work evaluated the integration of Concentrated Solar Power (CSP) with a sugarcane bagasse cogeneration plant located in Campo Grande (Brazil). The plant is equipped with two 170 t/h capacity steam generators that provide steam at 67 bar/525 °C. Superheated steam is expanded in a backpressure and in a condensing-extraction turbine. The evaluated hybridization layouts were: (layout 1) solar feedwater pre-heating; (layout 2) saturated steam generation with solar energy and post superheating in biomass steam generators and (layout 3) superheated steam generation in parallel with biomass boilers. Linear Fresnel and parabolic trough were implemented in layouts 1 and 2, while solar tower in layout 3. The exportation of electricity to the grid was increased between 1.3% (layout 1/linear Fresnel) and 19.8% (layout 3) in comparison with base case. The levelized cost of additional electricity was accounted between 220 US$/MWh (layout 3) and 628 US$/MWh (layout 1/linear Fresnel). The key factor related to layout 3 was the improvement of solar field capacity factor due to the solar-only operation of this approach. These aspects demonstrate that the combination of solar and bagasse resources might be the key to turn CSP economically feasible in Brazil.

Novel process for the rapid and efficient generation of superheated steam using a water-containing porous material

Heat treatment by superheated steam has been utilized in several industrial fields including sterilization, desiccation, and cooking. Saturated and superheated steam is used in a number of home appliances, such as humidifiers, steam cookers, and steam irons. In these applications, in order to save electricity, it is necessary to produce steam on demand. Therefore, quick start-up and cut-off responses are required. However, most electrically energized steam generators require a relatively long time to generate steam due to the large heat capacities of the water in the container. We proposed a new method using containing porous material to generate saturated or superheated steam quickly. Steam may be generated rapidly using containing porous material because the heat capacity of the water in the meniscus is extremely small. The main objective of the present work was to show the performance of rapid steam generator we proposed and experimentally investigate the effect of the effective thermal conductivity of the porous material on the rapid and efficient generation of saturated and superheated steam. As a result, in order to generate superheated steam quickly and efficiently, the generator should be constructed from low-thermal-conductivity material. The energy utilization efficiency was analyzed based on a simplified one-dimensional model of the heat and fluid flow in the porous material, the calculated results were shown to be in good agreement with the experimental results. Based on the proposed model for the energy utilization efficiency on steam generation, the proposed rapid superheated steam generator is suitable for miniaturization.

Combined heat loss analysis of solar parabolic dish – modified cavity receiver for superheated steam generation

In this article, a 3-D numerical modeling is carried out to determine combined convection and surface radiation heat losses from a modified cavity receiver of parabolic dish collector used as mono-tube boiler for sub-cooled, saturated and superheated steam generation conditions. The forced convection heat loss from the modified cavity receiver is estimated using Nusselt number correlation developed for the modified cavity receiver. The effect of receiver inclination (β), operating temperature (Tw), emissivity of the cavity cover (∊), thickness of insulation (tins) on the combined heat losses from the modified cavity receiver is investigated. The boundary conditions for wall temperature and insulation thicknesses are chosen to match the three steam generation conditions. It is found that the natural convection heat losses are higher at β=0° (receiver facing sideward) and lower at β=90° (receiver facing down) whereas the forced convection heat loss is higher at β=90° and lower at β=0°. The variation of radiation heat losses is marginal for all values of β and vary with Tw. The effect of various parameters such as receiver inclination, wind direction (φ), wind speed and diameter ratios on forced convection heat loss from the receiver has also been studied. The forced convection heat loss at lower wind speeds (<2.5m/s) is lower than the natural convection heat losses. The maximum heat losses occur at side-on wind direction (φ=0) followed by head-on wind directions (φ=30–90°) and back-on wind directions (φ=-90° to -30°). The heat losses vary with diameter ratios for different configurations of the receiver. The forced convection heat loss is 1.2–9 times higher than natural convection heat loss for diameter ratio (ratio of cavity diameter to aperture diameter, d/D)=0.4 at 5m/s and receiver inclinations varying from 0° to 90°. Nusselt number correlations have been proposed based on the numerical analysis to estimate the combined convective and radiative heat loss. The present study attempts to estimate natural convection, forced convection and surface radiation heat losses from the modified cavity receiver under various conditions.

501 管状火炎超小型過熱蒸気発生器の研究開発(OS1 循環型社会の構築に資する新燃焼技術,研究討論セッション)

501 管状火炎超小型過熱蒸気発生器の研究開発(OS1 循環型社会の構築に資する新燃焼技術,研究討論セッション)